Compressor Cooling System and Method of Use

ABSTRACT

A compressor cooling system for an air compressor includes an air compressor including an external surface; an enclosure for enclosing the air compressor inside the enclosure; an air passage formed on the inside of the enclosure between the enclosure and the external surface of the air compressor; multiple holes in the enclosure; and a negative pressure source coupled to the air passage for drawing air through the multiple holes and into the enclosure for cooling the compressor.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional PatentApplication 60/933,674 filed Jun. 8, 2007 under 35 U.S.C. 119(e). Thisapplication is incorporated by reference herein as though set forth infull.

FIELD OF THE INVENTION

The field of this invention relates to systems and methods for coolingcompact heat generating devices such as air compressors.

BACKGROUND OF THE INVENTION

Portable oxygen concentrators are commonly used in the home medicalmarket to treat ambulatory patients with chronic obstructive pulmonarydiseases. To make an oxygen concentrator portable, the oxygenconcentrator must be as small as possible and weigh as little aspossible while delivering sufficient concentrated oxygen gas flow to theambulatory patient.

An air compressor is used in an oxygen concentrator to supplyhigh-pressure feed air to a Pressure Swing Adsorption (PSA) Module orconcentrator. An air compressor generates heat during use and is cooledby a fan cooling system (fan mounted to a driveshaft of the compressor).The fan moves cooling air over an air compression chamber, therebycooling that portion of the device that is heated by the compression ofthe air and by friction. The fan may also be used to cool a motor of thecompressor. In order to prevent the noise from the compressor fromescaping outside the device, the compressor may be encased in asound-proof enclosure. The enclosure keeps compressor noise fromescaping and allows for the ingress and egress of cooling air.

The fan cooling system for an air compressor has the limitation that thefan speed is generally limited to the compressor speed, and the pressureand velocity that may be generated by the fan is limited by the diameterof the fan so that small compressors may not be adequately cooled.Furthermore, if the compressor cooling fan is required to force airthrough a filter, or through a tortuous path for noise abatement, anauxiliary fan is required. An additional electric fan can be used, butthese fans may be noisy and/or larger than the compressor.

SUMMARY OF THE INVENTION

To solve these problems and others, an aspect of present inventioninvolves a cooling system and method for a compact heat generatingdevice (e.g., air compressor) that may be used in a portable device suchas a portable oxygen concentrator. An enclosure surrounds the compressorfor noise abatement. The enclosure has a number of holes, nozzles, orjet ducts in it located opposite the areas that require cooling. Theseopenings cause jet impingement, which is the basis for this coolingscheme, at selective thermal hot spots. A blower sucks air from insidethe enclosure and blows it through a tortuous path to a location remotefrom the compressor housing. The negative pressure generated by theblower provides the motive force for the air jets. The diameter, shape,and flow rate of the jets are designed to provide for turbulent flow ofthe cooling air jets. The cooling air jets are of non-uniform length anddirection, thereby breaking up the sound waves emanating from thecompressor.

A further aspect of the invention involves a compressor cooling systemfor an air compressor. The compressor cooling system includes an aircompressor having an external surface; an enclosure for enclosing theair compressor inside the enclosure; an air passage formed on the insideof the enclosure between the enclosure and the external surface of theair compressor; multiple holes in the enclosure; and a negative pressuresource coupled to the air passage for drawing air through the multipleholes and into the enclosure for cooling the compressor.

Another aspect of the invention involves a method of using a compressorcooling system. The method includes imparting a negative pressure in theair passage with the negative pressure source, drawing air through themultiple holes and into the enclosure for cooling the compressor;creating turbulent air flow in the air passage with the multiple holes,cooling the compressor and reducing compressor noise; and expelling theair flow from the compressor cooling system with the negative pressuresource.

Further objects and advantages will be apparent to those skilled in theart after a review of the drawings and the detailed description of thepreferred embodiments set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simple schematic of an embodiment of a gas separationdevice, which is an exemplary system/environment for the compressorcooling system.

FIG. 2 is a simple schematic of an embodiment of a compressor and anembodiment of a compressor cooling system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIG. 1, a gas separation device 10 constructed inaccordance with an embodiment of the invention will first be describedbefore describing an embodiment of a compressor cooling system 100. Thegas separation device 10 and the cooling system 100 will be described inconjunction with cooling a compressor; however, in alternativeembodiments, the cooling system 100 may be used to cool other compactheat generating devices such as vacuum pumps, internal combustionengines, lasers, electronics, etc. The gas separation device 10 mayinclude an air compressor 20, which may be combination compressor/vacuumgenerator (hereinafter “compressor”), a Pressure Swing Adsorption (PSA)Module or concentrator 30, a measurement mechanism 40, and a flowcontrol mechanism 50.

In a preferred embodiment, the gas separation device 10 is a portableoxygen concentrator weighing in the range of 2-20 pounds. An exampleportable oxygen concentrator system that comprises the gas separationdevice 10 is shown and described in U.S. Pat. No. 6,691,702, which ishereby incorporated by reference herein as though set forth in full. Inparticular, the portable oxygen concentrator system 100 and describedwith reference to FIGS. 1-16, and especially FIGS. 1, 2, 12, 15, and 16,may be used as the gas separation device 10.

In use, a feed fluid such as ambient air may be drawn into thecompressor 20 and delivered under high pressure to the PSA Module 30. Ina preferred embodiment, the compressor 20 is a combination compressorand vacuum pump/generator. The vacuum generator is preferably driven bythe same motor as the compressor and is integrated with the compressor.The vacuum generator draws exhaust gas from the PSA module 30 to improvethe recovery and productivity of the PSA module 30. The PSA module 30separates a desired product fluid (e.g., oxygen) from the feed fluid(e.g., air) and expels exhaust fluid. Characteristics of the productfluid (e.g., flow/purity) may be measured by a measurement mechanism 40.Delivery of the product fluid may be controlled with the flow controlmechanism 50.

With reference to FIG. 2, an embodiment of a compressor cooling system100 for cooling the compressor 20 will be described. The compressorcooling system 100 includes a close-fitting plastic enclosure 120 thatencloses the compressor 20. The space between the outside of thecompressor 20 and the inside of the enclosure 120 forms an airgap/passage 125 for cooling air transfer there through.

The enclosure 120 is substantially air tight and includes multiple(i.e., more than one) holes, nozzles, or jet ducts 130 (hereinafter“holes”) that communicate with the air passage 125. There are no fluidinlets other than the holes 130, which are opposite to the portions ofthe compressor 20 (e.g., cylinder walls) that need cooling. The holes130 may be of various lengths and/or diameters so that the sound wavesemanating from the compressor 20 take different times to reach theoutside of the enclosure 120, thereby reducing the noise emitted fromthe compressor 20.

The inlet of a centrifugal blower 140 is connected to the air passage125, thereby maintaining a vacuum in the air passage 125 around thecompressor 20, drawing air in through the holes 130.

The size and flow rate of the air through the holes 130 may beadjusted/varied to keep the flow though the holes 130 and into the airpassage 125 turbulent so as to maximize heat transfer from thecompressor 20. The holes 130 are configured so that the Reynolds numberfor this air flow though the holes 130 and into the air passage 125 ismaintained above approximately 2000 in order to achieve turbulent flowand maximize heat transfer from the compressor 20.

A tortuous duct 150 is connected to the outlet of the centrifugal blower140. The blower exhaust may be routed through the tortuous duct 150 inorder to minimize the noise of the system.

The compressor cooling system 100 will now be described in use. Duringuse of the compressor 20 heat is generated by the compressor 20. Thecentrifugal blower 140 draws air out of the air passage 125 in theenclosure and blows it through the tortuous duct 150 to a locationremote from the compressor 20. The negative pressure generated by theblower 140 provides the motive force at the holes 130 (e.g., holes,nozzles, or jet ducts) for the creation of air jets onto and aroundopposite sides of the compressor 20 (e.g., cylinder walls) that needcooling. The diameter, shape, and configuration of the holes 130 and theflow rate through the system 100 are designed to provide for turbulentflow of cooling air jets in the passage 125. This cooling air jetimpingement is the basis for cooling the compressor 20 at selectivethermal hot spots. The cooling air jets are of non-uniform length anddirection, thereby breaking up the sound waves emanating from thecompressor 20.

The compressor cooling system 100 allows smaller compressor cooling fansor no compressor cooling fans to be provided in cooling the compressor20. The compressor cooling system 100 also reduces the need for anauxiliary cooling fan. With a smaller compressor cooling fan, thecompressor system takes up less space than in the past. The turbulentflow in the compressor cooling system 100 breaks up the sound wavesemanating from the compressor 20, reducing the noise from the compressorsystem. Since the cooling fan only adds heat and energy to the exhaustair leaving the compressor enclosure the cooling air delivered to thecompressor is cooler than it would be in the case of a fan providingpositive pressure to the compressor cooling system.

The above figures may depict exemplary configurations for the invention,which is done to aid in understanding the features and functionalitythat can be included in the invention. The invention is not restrictedto the illustrated architectures or configurations, but can beimplemented using a variety of alternative architectures andconfigurations. Additionally, although the invention is described abovein terms of various exemplary embodiments and implementations, it shouldbe understood that the various features and functionality described inone or more of the individual embodiments with which they are described,but instead can be applied, alone or in some combination, to one or moreof the other embodiments of the invention, whether or not suchembodiments are described and whether or not such features are presentedas being a part of a described embodiment. Thus the breadth and scope ofthe present invention, especially in the following claims, should not belimited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as mean “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; and adjectivessuch as “conventional,” “traditional,” “standard,” “known” and terms ofsimilar meaning should not be construed as limiting the item describedto a given time period or to an item available as of a given time, butinstead should be read to encompass conventional, traditional, normal,or standard technologies that may be available or known now or at anytime in the future. Likewise, a group of items linked with theconjunction “and” should not be read as requiring that each and everyone of those items be present in the grouping, but rather should be readas “and/or” unless expressly stated otherwise. Similarly, a group ofitems linked with the conjunction “or” should not be read as requiringmutual exclusivity among that group, but rather should also be read as“and/or” unless expressly stated otherwise. Furthermore, although item,elements or components of the disclosure may be described or claimed inthe singular, the plural is contemplated to be within the scope thereofunless limitation to the singular is explicitly stated. The presence ofbroadening words and phrases such as “one or more,” “at least,” “but notlimited to” or other like phrases in some instances shall not be read tomean that the narrower case is intended or required in instances wheresuch broadening phrases may be absent.

1. A compressor cooling system for an air compressor, comprising: an aircompressor including an external surface; an enclosure for enclosing theair compressor inside the enclosure; an air passage formed on the insideof the enclosure between the enclosure and the external surface of theair compressor; multiple holes in the enclosure; a negative pressuresource coupled to the air passage for drawing air through the multipleholes and into the enclosure for cooling the compressor.
 2. Thecompressor cooling system of claim 1, wherein the holes include at leastone of holes, nozzles, and jet ducts configured to deliver turbulent airflow into the air passage for cooling the compressor.
 3. The compressorcooling system of claim 2, wherein the turbulent air flow includes aReynolds number is above
 2000. 4. The compressor cooling system of claim1, wherein the holes are the only fluid inlets in the enclosurecommunicating with the air passage.
 5. The compressor cooling system ofclaim 1, wherein the air compressor includes opposite sides and theholes are directed at the opposite sides of the compressor.
 6. Thecompressor cooling system of claim 1, wherein the holes are configuredso that sound waves emanating from the air compressor take differenttimes to reach an outside of the enclosure, thereby reducing noiseemitted from the air compressor.
 7. The compressor cooling system ofclaim 1, wherein the negative pressure source is a centrifugal blower.8. The compressor cooling system of claim 7, wherein the centrifugalblower includes an outlet, and the compressor cooling system furtherincludes a tortuous duct connected to the outlet of the centrifugalblower for routing blower exhaust there through to minimize noise. 9.The compressor cooling system of claim 1, wherein the air compressor andcompressor cooling system is part of a pressure swing adsorptionconcentrator.
 10. The compressor cooling system of claim 9, wherein thepressure swing adsorption concentrator is a portable oxygenconcentrator.
 11. A method of using a compressor cooling system,comprising: providing the compressor cooling system of claim 1;imparting a negative pressure in the air passage with the negativepressure source, drawing air through the multiple holes and into theenclosure for cooling the compressor; creating turbulent air flow in theair passage with the multiple holes, cooling the compressor and reducingcompressor noise; expelling the air flow from the compressor coolingsystem with the negative pressure source.
 12. The method of claim 11,wherein the air compressor includes opposite sides and the holes aredirected at the opposite sides of the compressor, and the method furtherincludes creating turbulent air flow in the air passage on oppositesides of the compressor with the multiple holes.